This invention relates to a trailer for transporting containers containing particulate lading, and more particularly to such a trailer having a tiltable support frame thereon for gravity unloading of particulate lading from a container supported on the frame.
Particulate ladings, such as polycarbonate or thermoplastic materials, synthetic resins, and the like, are normally loaded within boxes, bags, containers or the like at a site where the plastic material is manufactured, and then transported by wheeled vehicle to a site where the plastic material is unloaded from the container into a storage facility for subsequent use in the manufacture of various plastic end products. It is highly desirable that such plastic materials or ladings, such as polyethylene pellets, not be contaminated by foreign matter or the like as even small amounts of foreign matter or contamination affect the quality of the subsequent manufactured products. Heretofore, plastic liners or bags such as vinyl or polyethylene liners have been used within containers to protect the lading from contamination. The plastic liners are normally sealed at the initial loading site and the lading is maintained in sealed relation within the plastic liner until unloaded at the unloading site, thereby insuring that the plastic lading will not be contaminated. Normally, the plastic lading is unloaded at the unloading site from the container by a suction or vacuum line extending within the container and then is conveyed pneumatically to a storage facility, such as bins, silos, or the like, until needed for the production of plastic end products. Pressurized air is sometimes used to push or aid in pushing the particulate plastic material from a container into a pneumatic discharge line for pneumatically conveying the plastic material into the storage facility.
In our prior U.S. Pat. No. 4,875,811 dated Oct. 24, 1989 a transportation system was shown for transporting plastic particulate material in a sealed condition from one location where the plastic lading is loaded into a plastic liner within a container to another location or site for unloading. The transportation system utilized a trailer for transport of the container between the two sites and for unloading the plastic material at the second site. The trailer included rear tandem wheels and a tiltable frame for unloading particulate lading from a plastic bag within the container upon tilting of the frame at an angle greater than the angle of repose of the material being unloaded.
It is noted that highway vehicles traveling over interstate highways are governed by U.S. Federal Regulations for bridges and this controls the design of such highway vehicles. Included in such bridge regulations are the requirements of a total weight of eighty thousand (80,000) pound for the tractor, trailer, and loaded container on the trailer. Thus, the so-called tare weight of the trailer is desired to be at a minimum in order for a loaded container thereon to carry a maximum amount of particulate lading within the container. The trailer having rear tandem wheels and axles shown in our aforementioned U.S. Pat. No. 4,875,811 was designed to be within such federal regulations but yet to carry a maximum amount of particulate lading. Containers of twenty (20) feet in length and having a lading weight of between around forty-two thousand (42,000) pounds and forty-five thousand (45,000) pounds are normally utilized for the transport of particulate lading, such as plastic pellets or the like, which are unloaded pneumatically at an unloading site.
Further, U.S. regulations control the length of a trailer with rear tandem axles and a maximum length of forty-two (42) feet is permitted. Thus, the pneumatic conveying apparatus for unloading the lading was carefully positioned between the rear end of the container and the rear tandem wheels in order to permit an effective and satisfactory gravity unloading of particulate lading from the rear end of the tilted container to a rotary valve which feeds the particulate lading into an air stream in a low hopper for pneumatic conveyance to a storage site such as a silo, for example. While it is desirable that the weight of the trailer be at a minimum, such trailers heretofore have been over around forty (40) feet in length and have utilized a pair of wheeled rear axles at the rear end of the trailer with the pneumatic discharge from the container being in front of the rear wheels.